Allylic chain transfer agents

ABSTRACT

A process for the free radical initiated polymerization of unsaturated species characterized by the use of compound of Formula (I) as chain transfer agents: ##STR1## wherein: X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR 6  ; C(O)NR 7  R 8  ; and halogen; 
     Q is selected from COOR 1  ; CN; and C(O)NR 7  R 8  ; 
     Y is selected from hydrogen; C 1  to C 6  alkyl; C 1  to C 6  alkyl substituted with one or more substituents selected from hydroxy, amino, C 1  to C 6  alkoxy, C 1  to C 6  alkoxycarbonyl, halogen, CN and optionally substituted aryl; C 1  to C 6  alkenyl; and C 1  to C 6  alkynyl; 
     Z is selected from COOR 2  ; CN; and optionally substituted aryl; 
     R 3  and R 4  are the same or different and are selected from hydrogen C 1  to C 4  alkyl and halogen; or R 3  and R 4  together with carbon atom to which they are attached form part of a carbocyclic or heterocyclic ring structure; and the other substituents are as defined in the text.

This invention relates to processes for radical-initiated polymerization of unsaturated species and for the control of molecular weight of the polymers produced from such processes. Polymers of low molecule weight, or oligomers, are important as precursors in producing other polymeric materials and such polymers have been found to be useful in a variety of products, for example, in the production of high solids (low VOC) surface coatings, in adhesives and as plasticizers in polymeric composites.

In conventional polymerization practice, the manufacture of oligomers requires the use of an initiator which acts as a free radical source, and of a chain transfer agent. The chain transfer agent controls the molecular weight of the polymer by reacting with the propagating polymer radical to terminate its growth. It then initiates a new polymer chain thus transferring the growth process from one discrete polymer molecule to another discrete polymer molecule.

The most commonly used chain transfer agents are alkanethiols, which normally are associated with an objectionable odour and lead to a wide distribution of molecular weight with certain monomers. Also, the residual thiols and the end thio-ether linkage of the polymers may have an adverse effect on the properties of the ultimate product from the polymer.

The present invention helps overcome the disadvantages of polymerizations regulated with thiols by using alternative polymerization regulators. These regulars have good stability and shelf life while maintaining many of the advantages over thiols. In the majority of cases, the materials that are part of the present process present a different range of chain transfer activities, allowing more opportunity for an optimal process to be selected for a given polymerization system of monomers and polymerization conditions. The chain transfer constant that a given regulator possesses is an important consideration in selecting the optimum process for producing low molecular weight polymers.

This invention provides a process for the free radical polygon of unsaturated species to provide polymers with lower molecular weight and narrower polydispersity characterised by the use of compounds of Formula (I) as chain transfer agents. ##STR2## wherein

X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR⁶ ; C(O)NR⁷ R⁸ ; and halogen;

Q is selected from COOR¹ ; CN; and C(O)NR⁷ R⁸ ;

Y is selected from hydrogen; C₁ to C₆ alkyl; C₁ to C₆ alkyl substituted with one or more substituents selected from hydroxy, amino, C₁ to C₆ alkoxy, C₁ to C₆ alkoxycarbonyl, halogen, CN and optionally substituted aryl; C₁ to C₆ alkenyl; and C₁ to C₆ alkynyl;

Z is selected from COOR² ; CN; and optionally substituted aryl;

R³ and R⁴ may be the same or different and are selected from hydrogen, C₁ to C₄ alkyl and halogen; or R³ and R⁴ together with the carbon atom to which they are attached form part of a carbocyclic or heterocyclic ring structure;

R is selected from C₁ to C₁₈ alkyl; C₁ to C₁₂ alkyl substituted with one or more substituents selected from hydroxy, amino, C₁ to C₆ alkoxy, phenyl halogen, NCO, CN, and COOR⁵ ;

R¹ and R² may be the same or different and are selected from C₁ to C₁₈ alkyl; C₁ to C₁₂ alkyl substituted with one or more substituents selected from hydroxy, C₁ to C₆ acyloxy, C₁ to C₆ alkoxy, amino, halogen, Si(R⁹)₃, Si(OR⁹)₃, optionally substituted aryl, CN and NCO;

R⁵ is selected from hydrogen and C₁ to C₆ alkyl;

R⁶ is selected from hydrogen and C₁ to C₁₈ alkyl;

R⁷ and R⁸ may be the same or different and are selected from C₁ to C₁₈ alkyl; and

R⁹ is selected from C₁ to C₁₈ alkyl; C₁ to C₁₈ cycloalkyl; and optionally substituted aryl.

A preferred group of compounds of Formula I are the malonates with Q=COOR¹ and Z=COOR² having the Formula (IA): ##STR3## wherein:

X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR⁶ ; C(O)NR⁷ R⁸ ; and halogen;

Y is selected from hydrogen; C₁ to C₆ alkyl; C₁ to C₆ alkyl substituted with one or more substituents selected from hydroxy, amino, C₁ to C₆ alkoxy, C₁ to C₆ alkoxycarbonyl, halogen, CN, optionally substituted aryl; C₁ to C₆ alkenyl; and C₁ to C₆ alkynyl;

R¹ and R² may be the same or different and are selected from C₁ to C₁₈ alkyl; C₁ to C₁₂ alkyl substituted with a substituent selected from hydroxy, C₁ to C₆ acyloxy, C₁ to C₆ alkoxy, amino, halogen, optionally substituted aryl, CN and NCO;

R³ and R⁴ may be the same or different and are selected from hydrogen; C₁ to C₄ alkyl; and halogen; and

R, R⁶, R⁷ and R⁸ are as defined above.

Another preferred group of compounds which possess high chain transfer activities are the compounds of Formula (IB) where Q=COOR¹ and Z is optionally substituted aryl: ##STR4## wherein:

X Y, R¹, R³ and R⁴ are as defined above; and

Z is optionally substituted aryl.

The term "optionally substituted aryl" is used herein to mean an aromatic carbocyclic group which may or may not be substituted with one or more substituents that do not interfere with the polymerization process. Such substituents include alkyl, hydroxyalkyl, aminoalkyl, carboxylic acid, ester, acyloxy, amide, nitrile, haloalkyl, alkoxy, phosphonate, sulfonate, silyl or silyloxy groups.

Preferred aryl groups are phenyl or naphthyl groups.

When X is halogen, chlorine or bromine are preferred.

When R³ or R⁴ is halogen, chlorine or fluorine are preferred.

The following compounds of Formula I are novel and form part of the invention:

ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate;

ethyl 2,4-bis(ethoxycarbonyl)-2-ethyl-4-pentenoate;

ethyl 2-benzyl-2,4-bis(ethoxycarbonyl)-4-pentenoate;

ethyl 2-ethoxycarbonyl-2-methyl-phenyl-4-pentenoate;

ethyl 2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl)-4-pentenoate; and

ethyl 2-phenyl-4-(t-butoxycarbonyl)-4-pentenoate.

The process of this invention uses the compounds of Formula (I) as alternatives to thiols or other chain transfer agents for the control of molecular weight. The process of this invention may be operated in a similar manner to conventional processes using thiols. The compounds of Formula I can be prepared easily from inexpensive starting materials. Unlike thiols, they do not, in general, possess an objectionable odour.

The materials of this invention exhibit unexpectedly good chain transfer activities in general. For example, compound ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate (Ib) of this invention possesses significantly higher activity when compared with the methyl 4-methoxycarbonyl-2,2-dimethyl-4-pentenoate (MMA dimer or dimethyl 2,2-dimethyl-4-methylene glutarate) (refer to Table 5) in methyl methacrylate, acrylate and styrene polymerizations. The advantages of this invention will become more apparent by referring to the illustrative non-limiting examples shown below.

Preparation of Chain Transfer Agents

The allylic malonate derivatives Formula (IA)! are synthesized in good to excellent yield in a one-step reaction between the corresponding allylic halides (II) and malonates (IIIA). The reaction is carried out in the presence of base and solvent. Acetonitrile, N,N-dimethylformamide (DMF), dried THF or diethyl ether are suitable solvents. Although many (inorganic and organic) bases are suitable, sodium hydride, sodium alkoxide, sodamide, potassium alkoxides are preferred bases. The use of sodium hydride is found to provide better results than sodium alkoxide for the synthesis of these types of compounds. ##STR5##

Similarly, the allylic compounds of Formula IB e.g., compound (Ii)! can be synthesized in good yield in a one-step reaction between the corresponding allylic halide (II) and arylacetate (IIIB). The reaction is carried out in the presence of base and solvent. ##STR6##

Typical compounds (Ia & Ib) used in the process of this invention and their preparation are further illustrated by the following non-limiting preparative examples.

PREPARATIVE EXAMPLE 1

Ethyl 2,4-bis(ethoxycarbonyl)-4-pentenoate (Ia)

Formula (IA), X=COOCH₂ CH₃ ; Y=R³ =R⁴ =H; R¹ =R² =CH₂ CH₃ !. Typical procedure!.

To a suspension of sodium hydride (80% dispersion in oil, 0.36 g, 12 mmol) in acetonitrile (10 mL), was added diethyl malonate (1.60 g, 10 mmol). The resulting suspension was allowed to stir at room temperature for 15 minutes. A solution of ethyl α-(bromomethyl)acrylate obtained from a modified of S. E. Drewes, G. Loizou and G. H. P. Roos, Synthetic Communications, 1987, 17(3), 291-298! (1.93 g, 10 mmol) in acetonitrile (5 mL) was then added slowly to the above suspension. Stirring was maintained for 2 hours and then the reaction mixture was poured into water, and extracted (3x) with diethyl ether. The extracts were combined and dried over anhydrous Na₂ SO₄, filtered and evaporated to dryness. Distillation of the crude product under reduced pressure gave (Ia) as a colourless liquid (b.p. ˜140° C./0.1 mmHg) (1.90 g, ˜70%). ¹ H-NMR (CDCl₃) δ(ppm) 1.21 (t, 6H), 1.25 (t, 3H), 2.85 (d, 2H), 3.67 (t, 1H), 4.15 (q, 4H), 4.20 (q, 2H), 5.60 (br. s, 1H) and 6.18 (br. s, 1H). ¹³ C-NMR (CDCl₃) δ(ppm) 13.98, 31.34, 50.76, 60.81, 61.37, 127.56, 136.68, 166.38 and 168.67.

PREPARATIVE EXAMPLE 2

Ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate (Ib)

Formula (IA), X=COOCH₂ CH₃ ; Y=CH₃ ; R³ =R⁴ =H; R¹ =R² =CH₂ CH₃ !.

This compound was prepared using a similar procedure to that described above. Pure ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate (Ib) was obtained (60% yield) after column chromatography on silica-gel (diethyl ether: n-hexane 1:4 as eluent). ¹ H-NMR (CDCl₃) δ(ppm) 1.20 (t, 6H), 1.25 (t, 3H), 1.33 (s, 3H, 2.95 (s, 2H), 4.15 (m, 6H), 5.56 (br. s, 1H) and 6.22 (br. s, 1H). ¹³ C-NMR (CDCl₃) δ(ppm) 13.91, 14.06, 35.98, 53.88, 60.78, 61.23, 128.61, 136.29, 166.67 and 171.57.

PREPARATIVE EXAMPLE 3

Ethyl 2,4-bis(ethoxycarbonyl)-2-ethyl-4-pentenoate (Ic)

Formula (IA), X=COOCH₂ CH₃ ; Y=CH₂ CH₃ ; R³ =R⁴ =H; R¹ =R² =CH₂ CH₃ !.

This compound was prepared in ˜80% yield using a similar procedure to that described in Example 1. ¹ H-NMR (CDCl₃) δ(ppm) 0.85 (t, 3H), 1.20 (t, 6H), 1.30 (t, 3H), 1.85 (q, 2H), 2.95 (s, 2H), 4.15 (m, 6H), 5.58 (br. s, 1H) and 6.25 (br. s, 1H). ¹³ C-NMR (CDCl₃) δ(ppm) 8.58, 14.06, 14.16, 25.46, 32.98, 58.32, 60.89, 61.15, 128.42, 136.53, 167.05 and 171.09.

PREPARATIVE EXAMPLE 4

Ethyl 2-benzyl-2,4-bis(ethoxycarbonyl)-4-pentenoate (Id)

Formula (IA), X=COOCH₂ CH₃ ; Y=CH₂ C₆ H₅ ; R³ =R⁴ =H; R¹ =R² =CH₂ CH₃ !.

This compound was prepared by a procedure similar to Example 1, using diethyl benzylmalonate as the starting material; the product was isolated in 76% yield as a colourless syrup. ¹ H-NMR (CDCl₃) δ(ppm) 1.20 (t, 6H), 1.30 (t, 3H), 2.95 (s, 2H), 3.25 (s, 2H), 4.15 (m, 6H), 5.65 (br. s, 1H), 6.25 (br. s, 1H) and 7.20 (m, 5H). ¹³ C-NMR (CDCl₃) δ(ppm) 13.82, 14.11, 30.40, 39.63, 43.30, 58.75, 60.84, 61.20, 126.87, 128.11, 128.55, 130.08, 167.40 and 170.56.

PREPARATIVE EXAMPLE 5

Ethyl 4-chloro-2-ethoxycarbonyl-2-methyl-4-pentenoate (Ie)

Formula (IA), X=Cl; Y=CH₃ ; R³ =R⁴ =H; R¹ =R² =CH₂ CH₃ !.

To a suspension of sodium hydride (25.2 g, 0.84 moles, 80% dispersion in oil) and diethyl methylmalonate (104.5 g, 0.60 moles) in acetonitrile (500 mL), a solution of 2,3-dichloropropene (66.6 g, 0.60 moles) in acetonitrile (100 mL) was added slowly over 20 minutes with stirring at room temperature. The resulting mixture was allowed to stir at room temperature overnight. Water (250 mL) was added, and the mixture extracted three times with diethyl ether (200 mL×3). The combined organic layers were washed successively with water (200 mL) and brine (200 mL), they were then dried over anhydrous MgSO₄. After removal of the organic solvent, distillation of the crude product under reduced pressure afforded the product (Ie) as a colourless liquid (91.6 g, 61.5% yield), b.p. 77°-78° C. (0.1 mmHg). ¹ H-NMR (CDCl₃) δ(ppm) 1.22 (t, 6H), 1.42 (s, 3H), 3.00 (s, 2H), 4.18 (q, 4H), 5.20 (s, 1H) and 5.30 (s, 1H).

PREPARATIVE EXAMPLE 6

Ethyl 2-ethoxycarbonyl-4-phenyl-4-pentenoate (If)

Formula (IA), X=Phenyl; Y=R³ =R⁴ =H; R¹ =R² =CH₂ CH₃ !.

This compound was prepared in ˜20% yield (not optimized according to a similar procedure to that described in Example 1. The reaction was carried out between α-(bromomethyl)styrene obtained from the reaction of α-methylstyrene and N-bromosuccinimide in carbon tetrachloride according to the published procedure by H. Pines, H. Alul and M. Kolobielski, J. Org. Chem., 1957, 22, 1113-1114! and diethyl malonate in the presence of sodium hydride (1 eq.). ¹ H-NMR (CDCl₃) δ(ppm) 1.25 (t, 6H), 3.10 (d, 2H), 3.50 (t, 1H), 4.17 (q, 4H), 5.15 (br. s, 1H), 5.35 (br. s, 1H) and 7.35 (m, 5H).

PREPARATIVE EXAMPLE 7

Ethyl 2-ethoxycarbonyl-2-methyl-4-phenyl-4-pentenoate (Ig)

Formula (IA), X=Phenyl; Y=CH₃ ; R³ =R⁴ =H; R¹ =R² =CH₂ CH₃ !.

This compound was prepared in ˜60% yield by reacting α-bromomethyl)styrene obtained by method of H. Pines, H. Alui, M. Kolobielski, J. Org. Chem., p. 1113 (1957)! and diethyl methylmalonate in the presence of sodium hydride (2 eq.) in acetonitrile solvent. ¹ H-NMR (CDCl₃) δ(ppm) 1.10 (t, 6H), 1.30 (s, 3H), 3.18 (s, 2H), 3.90 (m, 4H), 5.10 (br. s, 1H), 5.27 (br. s, 1H) and 7.30 (m, 5H).

PREPARATIVE EXAMPLE 8

Ethyl 2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl)-4-pentenoate (Ih)

Formula (IA), X=COOC(CH₃)₃ ; Y=CH₃ ; R³ =H; R⁴ =CH₃ ; R¹ =R² =CH₂ CH₃ !.

The starting material, t-butyl (Z)-2-bromomethyl-2-butenoate, was prepared via literature procedures H. Hoffman and J. Rabe, Helvetica Chimica. Acta, 67(2), p. 413 (1984)!.

A stirred solution of diethyl methylmalonate (1.5 g, 8.6 mmol) in distilled THF was cooled to -5° C. and sodium hydride (0.52 g) added portionwise. The resultant suspension was stirred below 0° C. for an hour, then t-butyl (Z)-2-bromomethyl-2-butenoate added dropwise. The mixture was stirred below 0° C. for a further two hours before being allowed to warm to room temperature and stirred overnight Solvent was removed under reduced pressure, water added and the product extracted with ether (3×50 ml), and the combined organic layers dried over anhydrous magnesium sulphate. Upon removal of ether under reduced pressure, a pale yellow oil was obtained (2.02 g, 72%). ¹ H-NMR spectrum revealed the presence of two isomers in a ratio of 4:1, with the preferred isomer being the major product (Ih). Column chromatography on silica gel (9:1, pet. spirit 40°-60° C.: ethyl acetate) gave slight separation of the two isomers. The fraction containing the highest level of ethyl-2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl) pent-4-enoate (Ih) was used for the following spectroscopic data. ¹ H-NMR (CDCl₃) δ(ppm): 6.25, s, 1H; 5.55, s, 1H; 4.2, m, 4H; 3.7, q, 1H; 1.2-1.6, m, 21H. ¹³ C-NMR (CDCl₃) δ(ppm): 171.7, 171.2, 166.6, 143.5, 125.2, 80.5, 61.1, 57.5, 36.7, 28.0, 17.5, 17.0, 14.0, 13.9.

PREPARATIVE EXAMPLE 9

Ethyl 2-phenyl-4-(t-butoxycarbonyl)-4-pentenoate (Ii)

Formula (IB), X=COOC(CH₃)₃ ; Y=R³ =R⁴ =H; R¹ =CH₂ CH₃ ; Z=phenyl!

The starting allylic bromide material, t-butyl 2-(bromomethyl)propenoate was prepared via a modified procedure of S. E. Drewes, G. Loizou and G. H. P. Roos, Synthetic Communication, 1987, 17(3), 291-298 using t-butyl acrylate.

Ethyl phenylacetate (6.66 g, 40.6 mmol) was dissolved in dry THF (20 mL) and sodium hydride (1.09 g, 36.5 mmol) added portionwise. The resulting suspension was stirred at room temperature for 30 minutes then cooled on ice while t-butyl 2-(bromomethyl)propenoate (4.49 g, 20.3 mmol) was added dropwise under nitrogen atmosphere. On completion of the addition, the reaction mixture was allowed to reach room temperature then heated under reflux for 8 hours. The THF solvent was removed under reduced pressure, water added and the product mixture extracted with diethyl ether (3×50 mL). After removal of organic solvent, the excess ethyl phenylacetate was removed by vacuum distillation and the residue was chromatographed on a silica-gel column using 5% ethyl acetate in petroleum spirit as eluent. The pure product (Ii) was obtained as a very pale yellowish liquid (2.5 g, 41%). ¹ H-NMR (CDCl₃) δ(ppm): 1.10, t, 3H; 1.45, s, 9H; 2.65, dd, 1H; 3.00, dd, 1H; 3.85, dd, 1H; 4.10, m, 2H; 5.35, s, 1H; 6.00, s, 1H; 7.25, s, 5H.

Operation of the Process

The process of this invention may be adopted by the users of conventional processes using thiols with little change to reaction conditions other than the substitution of the appropriate quantity of compound of general Formula (1) for the thiol. The proportion of compound of Formula (I) used may be in the range of 0.01 to 30 mole percent based on total monomer, with a preferred range of 0.1 to 10 mole percent

The process may be operated at any of the reaction conditions appropriate to free radical polymerization, i.e., temperatures from -100° C. to 200° C. and pressures from below atmospheric to substantially above atmospheric.

The polymerization process can be carried out in bulk, solution, emulsion, mupon or other conventional polymerization modes Source of radicals for polymerizations are well known in the art and they include α,α'-azobisisobutyronitrile, 4,4'-bis(4-cyanovaleric acid), 2,2'-azobis(2,4-dimethylpentanenitrile), benzoyl peroxide, t-butyl peroxybenzoate, ammonium persulfate, potassium persulfate.

Any unsaturated monomers susceptible to free radical polymerization may be used although it should be noted that the chain transfer constant will vary with the monomer used. Suitable unsaturated monomers include acrylic esters, methacrylic esters, vinyl esters, vinyl aromatics, unsaturated or polyunsaturated hydrocarbons, or mixtures of these. Examples of these monomers are methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, vinyl acetate, styrene, p-chloromethylstyrene, 2-vinylpyridine, 4-vinylpyridine, N-vinylpyrrolidone, vinyl halides of the formula CH₂ =CHX where X is Cl or F, vinylidene halides of the formula CH₂ =CX₂ wherein X is independently Cl or F, vinyl ethers CH₂ =CHOR where R is alkyl and allyl monomers such as allyl ethers, allyl carbonates or diallyl carbonates.

Compounds of general Formula (I) used in the process of this invention display an unexpected high activity in controlling molecular weight in polymerization reactions and have chain transfer constants that may be superior to those of thiols, particularly with styrene and acrylates. Their activity is such that their chain transfer constants can approach the optimum values of 1.0 for batch polymerizations and this activity is not as highly dependent as that of thiols on the structure of the propagating radical.

The process is applicable to the manufacture of synthetic rubbers, and other polymer formulations where reduced molecular weight aids processing and improves properties. The process can also be used to produce low molecular weight polymers, oligomers, macromonomers and functional polymers for a variety of applications such as high-solids surface coatings, paints, and adhesives. Furthermore, the process can be used to enable better control over the polymerization kinetics, e.g., delaying the onset of gelation in cross-linking systems.

The operation of this process is demonstrated by the following non-limiting examples. In these examples molecular weight measurements were performed on a Waters Associates liquid chromatograph equipped with differential refractometer and six μ-styragel columns of 10⁶, 10⁵, 10⁴, 10³, 500 and 100 Å pore size. Tetrahydrofuran solvent was used at a flow rate of 1 mL/min. Results were derived by comparison with polystyrene standards using the Chromatix GPC-1 program.

The conversions were determined from the mass of the polymer isolated after precipitation in solvents where appropriate or after removal of all the volatiles in vacuo, and after subtracting the mass of the chain transfer agent.

EXAMPLE 1

Polymerization of Methyl Methacrylate

α,α'-Azobisisobutyronitrile (23.4 mg) was dissolved in freshly distilled inhibitor-free methyl methacrylate (MMA) (25 mL). Aliquots (4 mL) were removed and added to ampoules containing weighed amounts of the allylic chain transfer agent of Formula (I). The contents of the ampoule were either degassed by three freeze-evacuate-thaw cycles and sealed under vacuum or by bubbling nitrogen through the solution. The mixtures were then polymerized at 60° C. for one hour. The contents of the ampoules were then added dropwise to methanol and the precipitated polymers were collected and dried in a vacuum oven to constant weight. A small portion of each polymer was examined by gel-permeation chromatography (GPC) to determine its molecular weight.

                  TABLE 1                                                          ______________________________________                                         Molecular Weight and Conversions for                                           Methyl Methacrylate Polymerizations                                            Carried Out in the Presence of Chain Transfer Agents (CTA)                                  Temp.    Time 10.sup.3  CTA!/                                                                         %                                          Entry CTA    (°C.)                                                                            (hr.)                                                                                Monomer!                                                                               Conv. M.sub.n.sup.#                        ______________________________________                                          1    Ia     60       1.00 0.00     15.80 327160                                2    Ia     60       1.00 10.20    14.70 287300                                3    Ia     60       1.00 22.80    13.30 253630                                4    Ib     60       1.00 0.00     14.95 159200                                5    Ib     60       1.00 16.80    13.35 104100                                6    Ib     60       1.00 31.30    12.80  89900                                7    Ib     60       1.00 68.30    11.20  58700                                8    Ic     60       1.00 0.00     16.30 254350                                9    Ic     60       1.00 14.32    12.10 195900                               10    Ic     60       1.00 28.37    9.95  190150                               11    Ic     60       1.00 56.73    8.30  153150                               12    If     60       1.00 0.00     14.72 266800                               13    If     60       1.00 9.82     2.44   89000                               14    If     60       1.00 19.64    1.30   64875                               15    If     60       1.00 38.58    1.22   50800                               16    Ig     60       1.00 0.00     11.49 299000                               17    Ig     60       1.00 9.89     4.48  113400                               18    Ig     60       1.00 19.03    0.42   91990                               19    Ig     60       1.00 36.34    1.47   57530                               20    Ii     60       1.00 0.00     12.74 248860                               21    Ii     60       1.00 9.89     11.52 131020                               22    Ii     60       1.00 18.15    11.61 100900                               23    Ii     60       1.00 34.50    10.30  71120                               ______________________________________                                          .sup.# Numberaverage molecular weight determined by GPC, calibrated with       polystyrene standards.                                                   

EXAMPLE 2

Polymerization of Styrene

Polymerizations of styrene (Sty) were carried out similarly for three hours at 60° C. α,α'-Azobisisobutyronitrile (21.6 mg) was dissolved in freshly distilled styrene (50 mL). Aliquots (10 mL) were removed and transferred to ampoules containing weighed amounts of chain transfer agent. After the degassing and polymerization, the contents of ampoules were poured into methanol and the precipitated polymers were collected, dried, and examined as before.

                  TABLE 2                                                          ______________________________________                                         Molecular Weight and Conversions for Styrene Polymerizations Carried           Out in the Presence of Allylic Malonate Chain Transfer Agents and MMA          Dimer (Methyl 4-methoxycarbonyl-2,2-dimethyl-4-pentenoate)                                    Temp.   Time  10.sup.3  CTA!/                                                                        %                                         Entry                                                                               CTA       (°C.)                                                                           (hr.)  Monomer!                                                                              Conv. M.sub.n.sup.#                       ______________________________________                                          1   Ia        60      3.00  0.00    9.80  130000                               2   Ia        60      3.00  13.20   8.40  119250                               3   Ia        60      3.00  26.20   9.30  114300                               4   Ib        60      3.00  0.00    8.30  127000                               5   Ib        60      3.00  14.86   4.20   20400                               6   Ib        60      3.00  32.78   3.65   12500                               7   Ib        60      3.00  43.11   3.20   11400                               8   Ih        60      3.00  0.00    8.4   103995                               9   Ih        60      3.00  8.75    6.3    43755                              10   Ih        60      3.00  16.90   5.8    28222                              11   Ih        60      3.00  30.40   5.2    18682                              12   Ii        60      3.00  0.00    9.0   112525                              13   Ii        60      3.00  9.01    8.3   102660                              14   Ii        60      3.00  18.35   7.4    89260                              15   Ii        60      3.00  38.69   6.5    80940                              16   MMA Dimer 60      3.00  0.00    10.5  120010                              17   MMA Dimer 60      3.00  12.50   7.0    59855                              18   MMA Dimer 60      3.00  25.00   5.8    41220                              19   MMA Dimer 60      3.00  49.88   5.7    27830                              ______________________________________                                          .sup.# Numberaverage molecular weight determined by GPC, calibrated with       polystyrene standards.                                                   

EXAMPLE 3

Polymerization of Acrylate Esters

Polymerizations of methyl acrylate (MA) (or ethyl acrylate, EA) were carried out using a stock solution prepared from α,α'-azobisisobutyronitrile (6.34 mg) and distilled thiophene-free benzene (25 mL). Aliquots (6 ml) were removed and added to ampoules containing freshly distilled methyl acrylate (4 mL), thiophene-free benzene (10 mL) and weighed amounts of the activated allylic malonate chain transfer agents. After degassing, the mixtures were polymerized at 60° C. for one hour; or at 80° C. for 30 minutes; or at 90° C. for 30 minutes. The volatiles were then removed on rotary evaporator and the polymers were dried in vacuo to constant weight and examined by GPC.

                  TABLE 3                                                          ______________________________________                                         Molecular Weight and Conversions for Acrylate Polymerizations                  Carried Out in the Presence of Chain Transfer Agents (CTA)                          Mono-          Temp. Time 10.sup.3  CTA!/                                                                        %                                       Entry                                                                               mer     CTA    (°C.)                                                                         (hr.)                                                                                Monomer!                                                                              Conv. M.sub.n.sup.#                     ______________________________________                                          1   MA      Ia     80    0.50 0.00    38.70 183900                             2   MA      Ia     80    0.50 10.00   36.60 137500                             3   MA      Ia     80    0.50 20.60   31.90  95750                             4   MA      Ia     80    0.50 39.75   25.60  67400                             5   EA      Ib     60    1.00 0.00    8.80  235,600                            6   EA      Ib     60    1.00 4.33    4.60   89400                             7   EA      Ib     60    1.00 5.87    3.85   53100                             8   EA      Ib     60    1.00 12.81   2.30   33500                             9   MA      Ie     60    1.00 0.00    26.3  493150                            10   MA      Ie     60    1.00 3.73    25.3  467300                            11   MA      Ie     60    1.00 14.67   21.8  362400                            12   MA      If     60    1.00 0.00    28.2  388450                            13   MA      If     60    1.00 9.43    ˜0.0                                                                            31455                            14   MA      If     60    1.00 20.61   ˜0.0                                                                            8140                             15   MA      If     60    1.00 34.18   ˜0.0                                                                            5810                             16   MA      If     80    0.50 0.00    46.0  133300                            17   MA      If     80    0.50 8.70    0.39   22630                            18   MA      If     80    0.50 18.10   1.60   11540                            19   MA      If     80    0.50 34.44   ˜0.0                                                                            4375                             20   MA      Ig     60    1.00 0.00    21.44 657800                            21   MA      Ig     60    1.00 8.84    0.47   13260                            22   MA      Ig     60    1.00 21.32   0.14   4885                             23   MA      Ig     60    1.00 37.33   0.0    3495                             24   MA      Ig     80    0.50 0.00    17.36 187500                            25   MA      Ig     80    0.50 9.43    0.30   7960                             26   MA      Ig     80    0.50 20.73   0.21   3860                             27   MA      Ig     80    0.50 38.79   0.12   2560                             28   MA      Ih     60    1.00 0.00    20.5  926632                            29   MA      Ih     60    1.00 6.54    22.6   66231                            30   MA      Ih     60    1.00 13.30   27.5   37180                            31   MA      Ih     60    1.00 26.50   12.9   21243                            32   MA      Ih     80    0.50 0.00    40.6  176925                            33   MA      Ih     80    0.50 6.91    38.3   48525                            34   MA      Ih     80    0.50 13.30   32.1   26285                            35   MA      Ih     80    0.50 26.50   28.4   16074                            36   MA      Ii     60    1.00 0.00    23.4  739090                            37   MA      Ii     60    1.00 7.49    3.2   151740                            38   MA      Ii     60    1.00 14.29   1.7    98120                            39   MA      Ii     60    1.00 29.24   0.2    52940                            40   MA      Ii     90    0.50 0.00    55.6   83145                            41   MA      Ii     90    0.50 6.93    20.9   46055                            42   MA      Ii     90    0.50 14.91   16.4   28680                            43   MA      Ii     90    0.50 28.99   14.9   18100                            ______________________________________                                          .sup.# Numberaverage molecular weight determined by GPC, calibrated with       polystyrene standards.                                                   

EXAMPLE 4

Polymerization of Vinyl Acetate

Polymerizations of vinyl acetate (VAc) were carried out in vacuo at 60° C. for one hour or at 80° C. for one hour using the following procedure. α,α'-Azobisisobutyronitrile (20.5 mg) was dissolved in freshly distilled vinyl acetate (25 mL). Aliquots (4 mL) were removed and added to ampoules containing weighed amounts of the chain transfer agents. After the polymerization, the volatiles were removed and the polymers were dried and examined as before.

                  TABLE 4                                                          ______________________________________                                         Molecular Weights and Conversions for Vinyl Acetate Polymerizations            Carried Out in the Presence of Chain Transfer Agents (CTA)                                  Temp.   Time  10.sup.3  CTA!/                                                                         %                                          Entry                                                                               CTA     (°C.)                                                                           (hr.)  Monomer!                                                                               Conv.  M.sub.n .sup.#                      ______________________________________                                         1    Ie      80      1.00  0.00     60.2   62700                               2    Ie      80      1.00  1.87     29.9   54700                               3    Ie      80      1.00  3.72     18.9   38300                               4    Ie      80      1.00  7.43     12.6   25900                               5    Ig      60      1.00  0.00     5.37   193500                              6    Ig      60      1.00  12.90    0.08   8200                                7    Ig      60      1.00  23.90    0.02   5740                                8    Ig      60      1.00  39.10    0.03   3260                                ______________________________________                                          .sup.# Polystyrene standard equivalent numberaverage molecular weight.   

Table 5 summarizes the results of chain transfer constants in polymerizations of common monomers using the allylic chain transfer agents (Ia), (Ib), (Ic), (Ie), (If), (Ig) and (Ih)!.

                  TABLE 5                                                          ______________________________________                                         Chain Transfer Constants (C.sub.x) for Polymerizations of Common               Monomers                                                                       in the Presence of Allylic Transfer Agents and MMA Dimer                                                   Chain Transfer Constants                           CTA      Monomer   Conditions                                                                              (C.sub.x)                                          ______________________________________                                         Ia       MMA       60° C.                                                                           0.004                                                       MA        80° C.                                                                           0.020                                                       Sty       60° C.                                                                           0.004                                              Ib       MMA       60° C.                                                                           0.015                                                       Sty       60° C.                                                                           0.148                                                       EA        60° C.                                                                           0.203                                              MMA      EMA       60° C.                                                                           0.007                                              Dimer    EA        60° C.                                                                           0.120                                                       Sty       60° C.                                                                           0.057                                              Ic       MMA       60° C.                                                                           0.004                                              Ie       VAc       80° C.                                                                           0.274                                                       MA        60° C.                                                                           0.005                                              If       MMA       60° C.                                                                           0.060                                                       MA        60° C.                                                                           0.450                                                       MA        80° C.                                                                           0.560                                              Ig       MMA       60° C.                                                                           0.040                                                       MA        60° C.                                                                           0.670                                                       MA        80° C.                                                                           0.850                                                       VAc       60° C.                                                                           7.010                                              Ih       MA        60° C.                                                                           0.150                                                       MA        80° C.                                                                           0.180                                                       Sty       60° C.                                                                           0.150                                              Ii       MMA       60° C.                                                                           0.029                                                       MA        60° C.                                                                           0.053                                                       MA        90° C.                                                                           0.130                                                       Sty       60° C.                                                                           0.009                                              ______________________________________                                    

EXAMPLE 5

Polymerization of Styrene

A multi-necked reactor was equipped with a stirrer, thermocouple, and condensor. The reactor was held under nitrogen positive pressure and the following ingredients were used.

    ______________________________________                                         Part 1                                                                         Styrene               2      ml                                                MEK                   4      ml                                                Transfer agent (Ib)   370    mg                                                Part 2                                                                         Styrene               8      ml                                                MEK                   12     ml                                                Part 3                                                                         AIBN                  l4     mg                                                MEK                   2      ml                                                Part 4                                                                         MEK                   2      ml                                                ______________________________________                                    

Part 1 was charged to the reactor and heated to 80° C. When the temperature stabilized at 80° C., part 2 (the monomer feed) was charged to the reactor concurrently with part 3 (the initiator feed) over 90 minutes via a syringe pump. Then part 4 was charged to the reactor as a single shot feed to rinse the syringe pump and the reaction mixture was held at 80° C. for further 120 minutes. The solvent and unreacted monomer were then distilled off. The result is summarized in Table 6.

                  TABLE 6                                                          ______________________________________                                                   CTA(Ib)   M.sub.n  M.sub.w                                                                               Dispersity                                 ______________________________________                                         Control    0        20400    39350  1.93                                       Example 5 370 mg    14900    29600  1.94                                       ______________________________________                                    

EXAMPLES 6-8

Polymerization of n-Butyl Methacrylate/Hydroxypropyl Acrylate

A multi-necked reactor was equipped with a stirrer, thermocouple, and condenser. The reactor was held under nitrogen positive pressure and following ingredients were used in three separate polymerizations.

    ______________________________________                                         PART   INGREDIENTS Example 6 Example 7                                                                              Example 8                                 ______________________________________                                         I.     Xylene      20.94 g   20.94 g 20.94 g                                          Transfer Agent Ib                                                                           0.00 g    3.47 g  6.94 g                                   II.    n-BMA       51.17 g   47.70 g 44.23 g                                          HPA         18.23 g   18.23 g 18.23 g                                   III.   Xylene       9.07 g    9.07 g  9.07 g                                          VAZO 67      0.60 g    0.60 g  0.60 g                                   ______________________________________                                    

Part I was charged to the reactor and heated to 90° C. When the temperature stabilized, Part II was charged to the reactor concurrently with Part III over 240 and 260 minutes, respectively. The reaction mixture was held for 60 minutes following the completion of the feeding of Part III. The monomer conversion was determined by solids analysis and molecular weight was determined by GPC. The results are summarized in Table 7.

                  TABLE 7                                                          ______________________________________                                         Example                                                                               Wt %                                                                    Number CTA(Ib)  Mn       Mw     Dispersity                                                                            Conversion                              ______________________________________                                         6      0        27180    65950  2.43   100%                                           (control)                                                               7      5.0%     16410    37940  2.31    98%                                    8      10.0%    12730    26750  2.10   100%                                    ______________________________________                                     

We claim:
 1. A process for the free radical initiated polymerization of ethylenically unsaturated monomer species characterised by the use of compounds of Formula (I) as chain transfer agents. ##STR7## wherein X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR⁶ ; C(O)NR⁷ R⁸ ; and halogen;Q is selected from COOR¹ ; CN; and C(O)NR⁷ R⁸ ; Y is selected from hydrogen; C₁ to C₆ alkyl; C₁ to C₆ alkyl substituted with one or more substituents selected from hydroxy, amino, C₁ to C₆ alkoxy, C₁ to C₆ alkoxycarbonyl, halogen, CN and optionally substituted aryl; C₁ to C₆ alkenyl; and C₁ to C₆ alkynyl; Z is selected from COOR² ; CN; and optionally substituted aryl; R³ and R⁴ may be the same or different and are selected from hydrogen, C₁ to C₄ alkyl and halogen; or R³ and R⁴ together with the carbon atom to which they are attached form part of a carbocyclic or heterocyclic ring structure; R is selected from C₁ to C₁₈ alkyl; C₁ to C₁₂ alkyl substituted with one or more substituents selected from hydroxy, amino, C₁ to C₆ alkoxy, phenyl, halogen, NCO, CN, and COOR⁵ ; R¹ and R² may be the same or different and are selected from C₁ to C₁₈ alkyl; C₁ to C₁₂ alkyl substituted with one or more substituents selected from hydroxy, C₁ to C₆ acyloxy, C₁ to C₆ alkoxy, amino, halogen, Si(R⁹)₃, Si(OR⁹)₃, optionally substituted aryl, CN and NCO; R⁵ is selected from hydrogen and C₁ to C₆ alkyl; R⁶ is selected from hydrogen and C₁ to C₁₈ alkyl; R⁷ and R⁸ may be the same or different and are selected from C₁ to C₁₈ alkyl; and R⁹ is selected from C₁ to C₁₈ alkyl; C₁ to C₁₈ cycloalkyl; and optionally substituted aryl.
 2. The process of claim 1 wherein X is a phenyl, substituted phenyl, chloro or bromo group.
 3. The process of claim 1 wherein Y is a phenyl or substituted phenyl.
 4. The process of claim 1 wherein R³ and R⁴ may be the same or different and are a chloro or fluoro group.
 5. The process of claim 1 wherein compounds of Formula (LA) are used as chain transfer agents. ##STR8## wherein Y, R, R⁶, R⁷ and R⁸ are as defined in claim 1;X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR⁶ ; C(O)NR⁷ R⁸ ; and halogen; Y is selected from hydrogen; C₁ to C₆ alkyl; C₁ to C₆ alkyl substituted with one or more substituents selected from hydroxy, amino, C₁ to C₆ alkoxy, C₁ to C₆ alkoxycarbonyl, halogen, CN, optionally substituted aryl; C₁ to C₆ alkenyl; and C₁ to C₆ alkynyl; R¹ and R² may be the same or different and are selected from C₁ to C₁₈ alkyl; C₁ to C₁₂ alkyl substituted with a substituent selected from hydroxy, C₁ to C₆ acyloxy, C₁ to C₆ alkoxy, amino, halogen, optionally substituted aryl, CN and NCO; and R³ and R⁴ may be the same or different and are selected from hydrogen; C₁ to C₄ alkyl; and halogen.
 6. The process of claim 5 wherein X is a phenyl, substituted phenyl, chloro or bromo group.
 7. The process of claim 5 wherein Y is a phenyl or substituted phenyl.
 8. The process of claim 5 wherein R³ and R⁴ may be the same or different and are hydrogen, chloro or fluoro groups.
 9. The process of claim 1 wherein compounds of Formula (IB) are used as chain transfer agents: ##STR9## wherein X, Y, R¹, R³ and R⁴ are as defined in claim 1; andZ is optionally substituted aryl.
 10. The process of claim 1 where the polymerisation occurs in solution.
 11. The process of claim 1 where the polymerisation occurs in an emulsified phase.
 12. The process of claim 1 when the unsaturated species are added before the polymerisation commences.
 13. The process of claim 1 when the unsaturated species are added during the reaction.
 14. The process of claim 1 when part of the unsaturated species are added before the start of the reaction and the remainder of the unsaturated species are added during the reaction.
 15. A compound of Formula (I) as defined in claim 1 which is selected from:ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate; ethyl 2,4-bis(ethoxycarbonyl)-2-ethyl-4-pentenoate; ethyl 2-benzyl-2,4-bis(ethoxycarbonyl)-4-pentenoate; ethyl 2-ethoxycarbonyl-2-methyl-4-phenyl-4-pentenoate; ethyl 2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl)-4-pentenoate; and ethyl 2-phenyl-4-(t-butoxycarbonyl)-4-pentenoate.
 16. A compound of Formula (1) as defined in claim 1 for use as a chain transfer agent in the free radical initiated polymerisation of unsaturated species.
 17. A chain transfer agent for use in the free radical initiated polymerisation of unsaturated species which comprises a compound of Formula (I) as defined in any one of claim
 1. 